Now I observe that when we are met together in the assembly, and the matter in hand relates to building, the builders are summoned as advisers; when the question is one of shipbuilding, then the ship-wrights; and the like of other arts which they think capable of being taught and learned. And if some person offers to give them advice who is not supposed by them to have any skill in the art, even though he be good-looking, and rich, and noble, they will not listen to him, but laugh and hoot at him, until either he is clamoured down and retires of himself; or if he persist, he is dragged away or put out by the constables at the command of the prytanes. This is their way of behaving about professors of the arts. But when the question is an affair of state, then everybody is free to have a say-carpenter, tinker, cobbler, sailor, passenger; rich and poor, high and low - any one who likes gets up, and no one reproaches him, as in the former case, with not having learned, and having no teacher, and yet giving advice; evidently because they are under the impression that this sort of knowledge cannot be taught.
Plato later built on this idea in The Republic to argue that rulership was a skill like any other, and that therefore we should be governed by experts. And he's been quoted approvingly by those who imagine themselves to be experts ever since. The problem is that this fundamentally misconstrues the nature of politics - politics isn't about finding the best solution to a predetermined goal, it's about deciding what that goal is. It's about ends rather than means, interests rather than management. The reason everybody is free to have a say is because everybody has interests, and nobody is qualified in any way to decide for others what those interests ought to be.